Shock metamorphism of plagioclase and amphibole (Experimental data)     

L. V. Sazonova  V. V. Milyavskii  T. I. Borodina  S. N. Sokolov  A. Z. Zhuk 《Izvestiya Physics of the Solid Earth》2007,43(8):707-712

The shock metamorphism of plagioclase and amphibole of various chemical compositions from amphibolite and granulite facies schists was studied in experiments with shock wave loading of samples in steel recovery ampoules of plane geometry. A maximum shock pressure was reached after a few circulations of waves in the sample (stepwise shock wave compression) and varied within 26–52 GPa. The recovered samples were examined by the methods of scanning electron microscopy and microprobe and X-ray phase analysis. It is established that an increase in the F, Ti, and K concentrations in amphibole and a decrease in the Ca concentration in plagioclase make these minerals more stable with respect to shock waves. It is shown that the migration of some chemical elements, starting already at the solid phase stage of transformation in plagioclase and amphibole, is intensified at the stage of melting. It is established that isotropization of plagioclase occurs through two different mechanisms. At relatively low pressures, it is caused by the fragmentation of substance at the microlevel and is accompanied by the formation of maskelynite, a typical mineral of meteorites and astrobleme rocks. At higher pressures, isotropization is associated with melting-induced amorphization.  相似文献   

Peraluminous granites frequently with mantle-like isotope compositions: the continental-type Murzinka and Dzhabyk batholiths of the eastern Urals   总被引：1，自引：0，他引：1  

A.?GerdesEmail author  P.?Montero  F.?Bea  G.?Fershater  N.?Borodina  T.?Osipova  G.?Shardakova 《International Journal of Earth Sciences》2002,91(1):3-19

Murzinka and Dzhabyk are continental-type batholiths of the middle and southern East Uralian domain. They comprise mainly undeformed peraluminous K-rich granites whose elemental composition is similar to some late-Variscan granites of western Europe, but with much more primitive Sr and Nd isotope ratios. Murzinka (254±5 Ma) is composed of silica-rich granites forming two different rock series with a ⁸⁷Sr/⁸⁶Sr_init of 0.709 and 0.704, respectively. Both series have enormous variations in εNd₂₅₅ (–11.9 to –0.1 and –8.9 to +4.1) that reveal derivation from heterogeneous sources. Dzhabyk (291±4 Ma) also comprises two coeval magmas which yielded voluminous granites and quartz-monzonites, respectively, with smaller differences in ⁸⁷Sr/⁸⁶Sr_init and εNd₂₉₀ (~0.7043, +0.8 to +1.6 and ~0.7049, 0.0 to +0.8). Despite their isotope compositions both batholiths lack evidence of genetic involvement of a mantle-derived parental magma. Moreover, we suggest that Dzhabyk granitoids were generated by polybaric partial melting of Paleozoic island-arc material, whereas Murzinka granitoids derived from an extremely heterogeneous source consisting mainly of Paleozoic and Proterozoic metagreywackes. This implies a relative fast reworking of juvenile arc crust and burial of the protoliths during the orogenic evolution of the Urals. Since there is neither evidence of significant extension, nor a direct link with subduction, we suggest that the main cause for late-orogenic anatexis was elevated heat production and fertility in the protolith, perhaps combined with some additional heat from unexposed mafic intrusions.  相似文献   

Transformations of rock-forming minerals under stepwise shockwave compression of quartz-feldspar-biotite-garnet schist from the Southern Urals     

I. V. Belyatinskaya  V. I. Fel’dman  V. V. Milyavsky  T. I. Borodina  A. A. Belyakov 《Moscow University Geology Bulletin》2012,67(1):30-42

Patterns in the shock metamorphic transformations of rock-forming minerals (garnet, biotite, plagioclase, and K-feldspar) in quartz-feldspar-biotite-garnet schist (the Southern Urals) that were subjected to shockwave compression using planar geometry recovery ampoules were investigated. The maximum shock pressures that were attained upon a few wave circulations in a sample (stepwise shock compression) reached 26, 36, and 52 GPa. Comparison of the transformations that occurred due to stepwise shock compression with diaplectic changes of the studied minerals in nature and in the course of experiments with convergent spherical shock waves revealed significant differences in the transformations of melanocratic (garnet and biotite) minerals under different types of loading.  相似文献   

Shock metamorphism of some rock-forming minerals     

V. I. Fel’dman  L. V. Sazonova  V. V. Milyavskii  T. I. Borodina  S. N. Sokolov  A. Z. Zhuk 《Izvestiya Physics of the Solid Earth》2006,42(6):477-480

The shock metamorphism of schist consisting of garnet, biotite, quartz, and plagioclase is studied under shock wave loading of a sample in steel recovery ampoules of plane geometry. A maximum shock pressure was reached during several circulations of waves in the sample (stepwise shock compression) and varied within the range 19–52 GPa. The recovered samples were examined by the methods of scanning electron microscopy and microprobe and X-ray phase analysis. The results were compared with natural impactites and with shock-induced alterations in minerals loaded by a spherical convergent wave. It is established that, given a plane geometry of loading (stepwise shock compression), solid-state transformations at the lattice level (migration of chemical elements and formation of shock thermal aggregates) are not observed in all of the studied minerals, in contrast to natural impact processes and spherical geometry experiments. Under the conditions of our experiments, minerals melt at higher pressures than in the case of natural impact processes and spherical geometry experiments. However, for each mineral studied, the mechanical strain patterns at close shock pressures are, on the whole, the same for all of the aforementioned three variants of shock wave loading.  相似文献   

Geodynamic settings and history of the Paleozoic intrusive magmatism of the central and southern Urals: Results of zircon dating     

G. B. Fershtater  A. A. Krasnobaev  F. Bea  P. Montero  N. S. Borodina 《Geotectonics》2007,41(6):465-486

The main stages of the Paleozoic intrusive magmatism in the Urals, 460–420, 415–395, 365–355, 345–330, 320–315, and 290–250 Ma, as well as two virtually amagmatic periods, 375–365 Ma (Frasnian-early Famennian) and 315–300 Ma (Late Carboniferous), are recognized. The Cambrian-Early Ordovician pause predated the onset of igneous activity in the Ural Orogen, while the Early Triassic pause followed by an outburst of trap magmatism postdated this activity. The interval from 460 to 420 Ma is characterized by mantle magma sources that produced ultramafic and mafic primary melts. The dunite-clinopyroxenite-gabbro association of the Platinum Belt and miaskite-carbonatite association are specific derivatives of these melts. The rift-related (?) Tagil Synform functioned at that time. The volcanic-plutonic magmatism in this oldest magmatic zone of the Uralides comprises gabbro, gabbro-granitoid, and gabbro-syenite series and comagmatic volcanic rocks. After a break almost 20 Ma long, this magmatism ended in the Early Devonian (405–400 Ma) with the formation of small K-Na gabbro-granitoid plutons. The magmatic intervals of 415–395, 365–355, and 320–315 Ma are characterized by the mantle-crustal nature. The first interval accompanied obduction of the oceanic lithosphere on the continental crust. The subsequent magmatic episodes presumably were related to the subduction of the island-arc (?) lithosphere beneath the continent and to the collision. The intense granitoid magmatism started 365–355 Ma ago. As in the following interval 320–315 Ma, the tonalite-granodiorite complexes, accompanied by hydrous basic magmatism, were formed. Amphibole gabbro and diorite served as a source of heat and material for the predominant tonalite and granodiorite. The Permian granitic magmatism had crustal sources. Thus, the mantle-derived Ordovician-Middle Devonian magmatism gave way to the mantle-crustal Late Devonian-Early Carboniferous plutonic complexes, while the latter were followed by the crustal Permian granites. This sequence was disturbed by rifting and formation of continental arcs accompanied by specific Early Carboniferous Magnitogorsk gabbro-granitoid series and Early Permian Stepnoe monzodiorite-granite series, which deviate from the general evolutional trend.  相似文献   

The Khao Que-Tam Tao gabbro-granite massif, Northern Vietnam: A petrological indicator of the Emeishan plume     

A. G. Vladimirov  P. A. Balykin  Phan Luu Anh  N. N. Kruk  Ngo Thi Phuong  A. V. Travin  Tran Trong Hoa  I. Yu. Annikova  M. L. Kuybida  E. V. Borodina  I. V. Karmysheva  Bui An Nien 《Russian Journal of Pacific Geology》2012,6(5):395-411

New data obtained on the Khao Que-Tam Tao gabbro-granite pluton (Northern Vietnam) are discussed. It was established that this pluton was formed at the Permian-Triassic boundary (250.5 ± 3.2 Ma, ⁴⁰Ar/³⁹Ar isotopic age). Morphologically, it represents a hypabyssal fracture intrusion. The first stage was marked by the intrusion of the picrobasaltic melt, the differentiation of which resulted in the formation of the layered peridotite-gabbro series and the quartz-bearing monzodiorites and granophyres in its endocontact at the final stage. At the second stage, the Khao Que peridotite-gabbro massif was broken in its central part by a fault, along which the Tam Tao granodiorite-granite massif was localized. Numerical simulation using the COMAGMAT program for the basic system and geochemical estimates for the granite system allow the statement that the mafic and granitic melts evolved independently, and their final products were quartz-bearing monzodiorite and granophyre, on the one hand, and aplites and pegmatites, on the other hand. The compositional correlation of the Permian-Triassic magmatic associations in Northern Vietnam (the Nui Chua gabbro pluton and the Khao Que-Tam Tao gabbro-granite and Pia Bioc granite plutons) and in Southeast China (flood basalts) allows these complexes to be regarded as a part of a single large igneous province produced by the Emeishan plume activity.  相似文献   

Water Chemistry Formation in Lakes of Specially Protected Natural Areas in the Altay Mountains: Case Study of the Mul’ta River     

Borodina  E. V.  Borodina  U. O. 《Water Resources》2019,46(4):582-594

Water Resources - Mass-spectrometry with inductively coupled plasma was applied to determine the dissolved forms of 26 elements in the water of lakes of the Mul’tinskii Basin. Specific...  相似文献   

Intrusive magmatism during early evolutionary stages of the Ural epioceanic orogen: U-Pb geochronology (LA ICP MS,NORDSIM, and SHRIMP II), geochemistry,and evolutionary tendencies     

G. B. Fershtater  A. A. Krasnobaev  F. Bea  P. Montero  N. S. Borodina 《Geochemistry International》2009,47(2):143-162

In recent years extensive data have been obtained on all geologically important intrusive complexes in the Central and Southern Urals by U-Pb zircon geochronologic high spatial resolution techniques (LA ICP MS, NORDSIM, and SHRIMP II). This made it possible to revise the current concepts for the magmatic activity of the Ural Paleozoic orogen.Intrusive magmatism that occurred early in the evolution of the Ural orogen was focused mostly in the Tagil megazone, was characterized by several common features, and took place nearly simultaneously within both of its zones: the Platinum Belt and the Tagil volcanic zone.The composition of the parental magmas of all complexes of this age corresponded to an ultramafic or mafic source; i.e., the magma was derived from a mantle source. The gabbroids most closely approximating the composition of the parental magmatic melts show geochemical features of suprasubduction melts, such as negative HFSE (Nb, Ti, and Zr) and positive Ba and Sr anomalies. The REE patterns of these rocks display variable La/Lu ratios, which are usually higher than 1. These geochemical features suggest that this magmatic source was a metasomatized mantle wedge, above which (at a depth of 40–25 km) a block of the pre-Ural basement occurred in Ordovician-Silurian time. The Tagil megazone started to develop on this block. By the Devonian, i.e., by the time when the Magnitogorsk zone began to evolve (～400 Ma) and continental-margin gabbro-tonalite-granodiorite magmatism was initiated (360 Ma), this basement had been destroyed by orogenesis. The major phases of Paleozoic magmatism in the Urals likely corresponded to global epochs of tectono-magmatic activity, because they correlate well with known data on the evolution of the ⁸⁷Sr/⁸⁶Sr ratio in Paleozoic seawater.  相似文献   

Comparison of petrology and isotope geochemistry of the Bulka peridotite–gabbro massif and granitoids of the Kyzykchadra complex (West Sayan)     

E. V. Borodina  A. E. Izokh  A. A. Mongush 《Geochemistry International》2016,54(4):321-345

The study provides new petrologic and isotope geochemical data for rocks of the 465 ± 5 Ma Bulka massif (Borodina et al., 2011). The primary amphibole from granitoid stocks cutting across the layered series of the massif yielded an Ar–Ar age of 415.9 ± 3.7 Ma. The rocks of the Bulka massif have ¹⁴³Nd/¹⁴⁴Nd ratio of 0.513243 and εNd (Т) values of +12.00. The granitoids have ¹⁴³Nd/¹⁴⁴Nd ratios between 0.512919 and 0.512961 and εNd (Т) values between +8.03 and +9.25. The Nd isotope composition indicates that the rocks of the Bulka massif and granitoids were derived from a depleted mantle source. Depletion of the rocks of the massif in LILE, LREE, and HFSE over LILE is inherited from the mantle source, which has geochemical signatures of N-MORB and subduction-related components. Granitoids are metaluminous I-type granites, which were probably generated either by differentiation of intermediate to mafic mantle-derived magmas or by melting of metabasites. The rocks of the granitoid stocks are characterized by enrichment in LILE and LREE and depletion in HFSE over LILE, which suggests derivation from arc-related parental magmas.  相似文献   

Sm-Nd and Rb-Sr ages of gabbroids,granitoids, and titanomagnetite ores from layered intrusions of the Kusa-Kopan Complex (South Urals)     

V. V. Kholodnov  G. B. Fershtater  Yu. L. Ronkin  N. S. Borodina  S. V. Pribavkin  O. P. Lepikhina 《Doklady Earth Sciences》2010,432(2):732-736

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